Rudy Severns wrote:
> If you use the 4" irrigation tubing there is an option on the wall
> thickness. They sell what is called "torque tube" for use on the moving
> irrigation equipment. In the 4" size the wall thickness is increased to
> 0.070" and the alloy is harder.
>
> This is what I used for my 80' top-loaded 160m array. It is heavier to
> raise but is really nice and stiff.
>
> 73, Rudy N6LF
Nothing wrong with that at all, in fact my first 90 ft mast was
all 4 inch. But I have since found that I can get away
with 90 feet, where the bottom 30 feet is 4 inch 0.050 wall, the
middle 30 feet is 3 inch 0.050 wall, and top 30 feet is 2 inch
0.050 wall. I raise it with a 30 ft falling derrick made of
4 inch tubing. There is a lot of strain at the joints, so I
developed an extra strong joint design to handle it. I got
most of my tubing used, and around here, all the stuff is 0.050
wall, since the way it is used is to just lay it on the ground.
They don't do those circle things here.
Note that going to thicker wall doesn't help with sag during
raising, since the extra weight cancels out the advantage of additional
thickness.
Rick N6RK
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